1. Technical Field
The present invention relates to an optical element including a functional layer between a first translucency member and a second translucency member, a display apparatus including an optical element, and a method for manufacturing an optical element.
2. Related Art
At the time of manufacturing an optical element including a functional layer between two translucency members, a method for bonding the two translucency members by an adhesive after forming the functional layer on one of the two translucency members, is adopted. For example, when a dichroic mirror is manufactured, after forming the functional layer on an inclined face of a first prism, the inclined face of a second prism is bonded to the inclined face of the first prism by the adhesive (see JPA-2006-154388 and JP-A-2004-317828). Furthermore, in JPA-2006-154388, forming a silicon oxide layer on the inclined face of the second prism, and thereby improving a wavefront aberration and wettability of a thermosetting adhesive such as an epoxy resin, are disclosed.
Since the prisms according to JP-A-2006-154388 and JP-A-2004-317828 are made of inorganic materials, there are problems that it is not possible to achieve a weight reduction in the optical element and a degree of freedom in shape is low.
Here, the inventors propose to configure an optical element by using the translucency member manufactured of resin as at least one of the two translucency members. Moreover, the inventors propose to configure an optical element by using the translucency member made of cyclo olefin polymer or cyclo olefin copolymer, paying attention to cyclo olefin polymer or cyclo olefin copolymer having characteristics that transmittance is high and degradation due to moisture absorption is less likely to occur.
However, since a surface of the translucency member which is made of cyclo olefin polymer or cyclo olefin copolymer is inactive, adhesive properties are poor. On the other hand, when the translucency members which are manufactured of resins are bonded by the adhesive, it is general to improve adhesive strength by surface reforming such as light irradiation depending on a low pressure mercury lamp, irradiation with excimer ultraviolet light, plasma irradiation, and corona electric discharge. However, if the surface treatment is performed, the transmittance is decreased due to transmutation, and thus it is not suitable for manufacturing the optical element. For example, the translucency member which is made of cyclo olefin copolymer has transmittance properties indicated as a line L0 in FIG. 7, but if the light irradiation is performed depending on the low pressure mercury lamp, the transmittance is decreased to a level indicated as a line L1. Furthermore, if the irradiation with the excimer ultraviolet light is performed, the transmittance is decreased to a level indicated as a line L2.